It may be difficult to focus with auto focus in the following situations :

Subject with low contrast

Excessively bright light in center of frame

Subject containing no vertical lines

In case of horizontal lines, just use the focus and reframe technique : focus on anther object located at a similar distance, or rotate the camera 45 degrees. Or, in adt ressort, use manal focusing. I see no problem there. This is the way the contrast detect auto focus is working. Each tool has its limitation, just chose the tool working bet for you.

Peter Heckert2 wrote:

Following two images are shot with an E-M5, a Panasonic 100- 300 and using digital Teleconverter 2x.

The first image is shot in landscape orientation. The camera had a hard time to put the cable in focus, and as you see, the resulting image is not sharp.

The second image is taken in portrait orientation. The camera found focus in the twinkling of an eye, and as you can see, the image is as sharp as it could be under these circumstances.

I can reproduce this behaviour each and every time with my E-M5 and also with my Panasonic G3.

These MFT cameras behave like an SLR, that has no cross sensors, but horizontal line sensors only! They focus on vertical lines only!Now, any SLR I know has vertical line sensors and thus will focus preferrably on horizontal details.There is no SLR that behaves like these MFT cameras.

Now, what is the better behaviour. If you think about moving objects, these will move horizontal in most cases. So it is much easier and more accurate to get focus on horizontal lines than on vertical lines in most cases.

So I think, the SLRs do it right and MFT generally has an unfortunate arrangement of focus sensors (which are implemented in software).

Focus is unsharp, focussing is awfully slow.

Focus is tack sharp. Focussing was spot on and lightning fast.

I believe, MFT has an issue with focus sensor orientation. It does it in the wrong way.

yes most movements are made in the horizontal direction, but on the other hand most things including men are standing vertically. So I think that we may have more problems focusing if it was the other way around. All the more so that CDAF doesn't like moving targets.